Step-by-step linear drive



STEP-BY-STEP LINEAR DRIVE Harold D. Gaite, Taplow, England, assignor to British Telecommunications Research Limited, Taplow, England, a British company Application December 19, 1952, Serial No. 326,981

Claims priority, application Great Britain December 31, 1951 7 Claims. (Cl. 271-25) The present invention relates to a mechanism for producing a step-by-step linear drive and while it has particular application to a mechanism for use in the telecommunication art, it is to be understood that it is not limited thereto.

A number of arrangements are known for producing a step-by-step linear drive and usually these known arrangements include a ratchet wheel, a detent wheel, and a drive Wheel.

The object of the invention is to provide a linear drive arrangement operating in a step-by-step manner which is simple in operation and cheaper to manufacture than the known types.

According to the invention, one end of a drive member is adapted to move in a substantially rectangular path in response to the reciprocating movement of an actuating member due to the provision of driving means controlled by said actuating member and mechanical constraining means cooperating with springs which are brought into operation successively as a result of the preceding movement of the drive member.

In a preferred embodiment of the invention two actuating levers form the driving means and the operation of one of them under the control of the actuating member serves to move the drive member in one direction where upon two springs come into operation successively to move the drive member first in a direction substantially perpendicular to the first direction and second in a direction parallel and opposite to the first direction while finally the operation of the second actuating lever serves to move the drive member hack to its starting position.

Preferably the actuating member comprises the armature or an extension of the armature of an electromagnet and the two actuating levers are pivoted on the armature or extension.

The invention will be better understood from the following description of one embodiment taken in conjunction with the accompanying drawings comprising Figs. 1 to 4, in which:

Fig. 1 shows the mechanism while Figs. 2, 3 and 4 show the mechanism in the position it occupies at the end of each successive stage of operation. For simplification the electromagnet has been omitted from .Figs. 2, 3 and 4.

Referring now to Fig.

in its position of rest,

1, the mechanism comprises a drive member pivoted on a link 11 which in turn is mounted on a fixed pivot at 12. Pivotally mounted on the other end of the link 11 is a member 13 the purpose of which will be described later. The drive member 10 and the member 13 are mounted between two fixed abutments 14 and 15 and the drive member 10 is acted upon by actuating levers 16 and 17. The actuating lever 16 is pivoted at 18 to the armature 19 of an electromagnet. This electromagnet can be of any known type and as shown consists of a coil 20 associated with an L-shaped yoke 21 to which the armature 19 is pivoted at 39. Restoration of the armature is effected by a spring 40 nited States Patent 0 connected between a pin 41 on the tail of the armature and a pin 42 on the yoke 21. The actuating lever 17, which is in the form of a bell crank lever is also pivoted to the armature 19 at the point 18 and is slotted to enable it to rotate about the pin 22.

The actuating lever 16 is spring-urged against a fixed abutment 23 by means of a spring 24 secured to the fixed pin 25. A second spring 26 is also secured to the pin 25 and to the drive member 10 at the point 27. The actuating lever 17 carries an arm 28 and a spring 29 extends between the point 30 on the arm and the point 27 on the drive member 10.

The abutment member 15 is provided with a recess within which a pawl 31 is pivotally mounted at 32, the pawl being urged against the upper surface of the recess by means of a leaf spring 33. In the position shown in Fig. 1, the end of this pawl engages a shoulder 34 of the drive member 10. It will thus be seen that the drive member 10 is acted upon by two springs, firstly by the spring 26 which tends to draw the drive member 10 downwardly and secondly by the spring 29 which tends to draw the drive member 10 towards the right. The downward movement is, however, prevented by the engagement of the actuating lever 16 under the head of the drive member 14 while the movement towards the right is prevented by the engagement of the pawl 31 with the shoulder 34 of the drive member 10.

The electromagnet will be operated from the earthed battery B when the interrupter contacts I next close after the switch S has been thrown. On the operation of the electromagnet, the armature 19 is attracted towards the coil against the tension of the spring 40, thus causing an upward movement of the actuating lever 16. This causes the drive member to move in an upward direction, and this movement will be referred to as the first movement of the drive member. Simultaneously the actuating lever 17 moves in a clockwise direction about the pivot 22, thereby increasing the tension in the spring 29. As the drive member 10 approaches the end of the first movement, the shoulder 34 becomes free of the pawl 31 as shown in Fig. 2. The spring 29 now comes into operation to move the drive member 10 towards the right, that is to say in a direction substantially perpendicular to the direction of the first movement. This second movement is terminated by engagement between the drive member 10 and the surface 43 of the abutment 15. This position is shown in Fig. 3. Toward the end of this second movement the head of the drive member 10 moves off the end of the actuating lever 16, thereb enabling the spring 26 to come into operation and draw the drive member 10 downwardly. This forms the third movement of the drive member which then takes up the position shown in Fig. 4.

The mechanism remains in this position until the interrupter contacts I open, and the electromagnet is deener ized whereupon the armature 19 is restored by the spring 46 and the actuating lever 17 performs an anticlockwise movement about the point 22. Surface 35 therefore moves the drive member 10 towards the left, this movement being the fourth in the cycle. Initially the fourth movement of the drive member 10 carries the actuating lever 16 with it, but, as this lever moves downwardly on the restoration of the armature, the position will be reached towards the end of the movement when the actuating lever 16 again moves underneath the head of the drive member under the influence of the spring 24. Similarly during the final movement the pawl 31 will eventually reengage with the shoulder 34 in the driving member 10 and the mechanism will be returned to the position shown in Fig. 1.

The mechanism described above, while it has a number of applications, has been particularly devised for driving the tape in step-by-step tape readers used in automatic transmitting heads in teleprinter working. For this purpose the head of the drive member is provided with pins 36 which engage with correspondingly spaced holes in the tape. The member 13 to which reference has already bene made, is provided to retain a positive control over the tape at all times. It will be seen that owing to the connection of the drive member and the member 1.3 at opposite ends of the link 11 the member 13 with its pins 37 will en age the tape when the pins on the drive member 10 do not and vice versa. The member 13 is subjected only to an up and down movement and is preferably confined between the fixed abutment 14 and an additional fixed abutment 38.

It will thus be seen that the invention provides an extremely simple and eifective mechanism which can be manufactured cheaply and is yet sufiiciently robust to perform the operation required.

I claim:

1. A step-by-step linear drive mechanism for causing a drive member to perform a substantially rectangular movement, comprising a movable support, means for rigidly securing said drive member to said support, operating means effective on said support to move said drive member in one direction, first spring means effective on said support to move said drive member at right angles to the first direction of movement, first constraining means for preventing said first spring means from producing such movement until said drive member has moved a predetermined distance in said first direction, second spring means eiiective on said support to move said drive member in the opposite direction to said first movement, second constraining means for preventing said second spring means from producing such movement until said drive member has moved a predetermined distance at right angles thereto and third spring means effective on said support to move said drive member at right angles to said first direction of movement in the opposite direction to its previous right angle movement.

2. A step-by-step linear drive mechanism for causing the operative end of an elongated drive member to perform a substantially rectangular movement comprising operating means for moving said drive member in the direction of its length, a first spring arranged to urge the operative end of said drive member at right-angles to its length, first constraining means for preventing such movement until said drive member has moved a predetermined distance in the direction of its length, a second spring arranged to urge said drive member in the direction of its length in the opposite direction to its previous lengthwise movement, second constraining means for preventing said second spring producing said movement until the operative end of said drive member has moved a predetermined distance at right-angles to its length under the action of said first spring, and means for moving the operative end of said drive member at right-angles to its length in the opposite direction to its previous right angle movement.

3. A step-by-step linear drive mechanism for causing the operative end of an elongated drive member to perform a substantially rectangular movement comprising an actuating arm, means for imparting reciprocating movement to said arm, a bar pivotally attached to said actuating arm and arranged to move said drive member in the direction of its length When said arm is moved in one direction, a first spring arranged to urge the operative end of said drive member at right-angles to its length,

first constraining means for preventing such movement until said drive member has moved a predetermined distance in the direction of its length, a second spring arranged to urge said drive member in the direction of its length in the opposite direction to its previous lengthwise movement, second constraining means for preventing said second spring producing said movement until the operative end of said drive member has moved a predetermined distance at right-angles to its length under the action of said first spring, and a lever pivotally attached to said actuating arm and arranged to move the operative end of said drive member at right-angles to its length in the opposite direction to its previous right angle movement when said actuating arm is moved in the other direction.

4. A step-by-step linear drive mechanism for causing the operative end of an elongated drive member to perform a substantially rectangular movement, comprising an electromagnet, an armature for said electromagnet, a first spring for restoring said armature to normal, means for intermittently energising said electromagnet to cause the intermittent operation and restoration of said armature, a bar pivotally attached to said armature and arrange to movesaid drive member in the direction of its length when said electromagnet is energised, a second spring arranged to urge the operative end of said drive member at right-angles to its length, first constraining means for preventing such movement until said drive member has moved a predetermined distance in the direction of its'length, a third spring arranged to urge said drive member in the direction of its length in the opposite direction to its previous lengthwise movement, second constraining means for preventing said third spring from producing said movement until the operative end of said drive member has moved a predetermined distance at right-angles to its length under the action of said second spring, and a lever pivotally attached to said armature and arranged to move the operative end of said drive member at right-angles to its length in the opposite direction to its previous right angle movement when said electromagnet is de-energised and said armature is restored to normal by said first spring.

5. A step-by-step linear drive mechanism as claimed in claim 2 in which said first constraining means comprises a spring-loaded pawl which is displaced as a result or the second movement of the drive member in the direction of its length and restores to its initial position on the completion of the movement of the drive member to its initial position.

6. A tape reading machine employing a linear drive mechanism as claimed in claim 4 in which the operative end of the drive member is provided with pins for engaging in suitable holes in a punched tape. A

'7. A tape reading machine as claimed in claim 6 comprising in addition a retaining member also provided With pins for engaging in said holes in said punched tape and a lever system connecting said drive member and said retaining member whereby when said drive member moves in the direction of its length said retaining member moves in the opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS 1.327520 Browning Jan. 6, 1920 1,798,072 Debrie Mar. 24, 1931 2,278,196 Fluharty Mar. 31, 1942 

